void plot_t_xsecs(){
  ifstream phifile("phi_t_yields.dat");
  double phi_3pi[8][100];
  double dphi_3pi[8][100];
  for (int j=0;j<100;j++){
    for (int k=0;k<8;k++){
  phifile >>  phi_3pi[k][j];
  phifile >> dphi_3pi[k][j];
  cout << phi_3pi[k][j] << endl;
  }
  }
  phifile.close();

  
  double eff[8][100],deff[8][100];
  ifstream infile("phi_eff_t.dat");
  for (unsigned int i=0;i<100;i++){
    for (unsigned int j=0;j<8;j++){
      infile >> eff[j][i];
      infile >> deff[j][i];
    }
  }
  infile.close();
  double phi_corr[8][100],dphi_corr[8][100];
  for (unsigned int i=0;i<100;i++){
  for (unsigned int j=0;j<8;j++){
    phi_corr[j][i]=phi_3pi[j][i]/(eff[j][i]+0.0000001);
    dphi_corr[j][i]=phi_corr[j][i]*sqrt(dphi_3pi[j][i]*dphi_3pi[j][i]
					/(phi_corr[j][i]*phi_corr[j][i])
					+deff[j][i]*deff[j][i]
					/((eff[j][i]+0.0000001)
					  *(eff[j][i]+0.0000001)));
//    cout << phi_3pi[j][i] << endl;
  }  
  }
  double t[100],dt[100];
  for (unsigned int i=0;i<100;i++){
    t[i]=0.02+0.04*i;
    dt[i]=0.02;
  }
  double tslopes[8];
  double errtslopes[8];
  double Egamma[8]={7.3,7.9,8.5,9.1,9.7,10.3,10.9,11.5};
  double dEgamma[8]={0.3,0.3,0.3,0.3,0.3,0.3,0.3,0.3};
  /*
  TGraphErrors *eg0=new TGraphErrors(100,t,eff[0]);
  eg0->Draw(); 
  TGraphErrors *eg1=new TGraphErrors(100,t,eff[1]);
  eg1->Draw();
   
  /*
  TGraphErrors *yg0=new TGraphErrors(100,t,phi_3pi[0],dt,dphi_3pi[0]);
  yg0->Draw(); 
  TGraphErrors *yg1=new TGraphErrors(100,t,phi_3pi[1],dt,dphi_3pi[1]);
  yg1->Draw(); 
  */
  TCanvas *myc9=new TCanvas("myc9");
  myc9->Draw(); 
  TH2F *h9=new TH2F("h9","E_{#gamma}=8.20-8.80 GeV",100,0,1.4,100,0,12000.); 
  h9->SetXTitle("-t [GeV^{2}]");
  h9->SetYTitle("Yield [counts / 0.04 GeV^{2}");
  h9->Draw();
  TGraphErrors *yg2=new TGraphErrors(100,t,phi_3pi[2],dt,dphi_3pi[2]);
  yg2->Draw("same,p"); 

  TCanvas *myc1=new TCanvas("myc1");
  myc1->Draw();
  
  TH2F *h1=new TH2F("h1","h1",100,0,1.4,100,0,20000.);
  h1->Draw();
	
  TGraphErrors *g0=new TGraphErrors(100,t,phi_corr[0],dt,dphi_corr[0]);
  g0->Draw("same");
  TF1 *f1=new TF1("f1","expo",0.1,1.);
  g0->Fit("f1","R");
  cout << g0->GetFunction("f1")->GetParameter(1) << endl; 
  cout << g0->GetFunction("f1")->GetParError(1) << endl;
  tslopes[0]=-g0->GetFunction("f1")->GetParameter(1);
  errtslopes[0]=g0->GetFunction("f1")->GetParError(1);
  
  TCanvas *myc2=new TCanvas("myc2");
  myc2->Draw();
  
  TH2F *h2=new TH2F("h2","h2",100,0,1.4,100,0,40000.);
  h2->Draw();

  TGraphErrors *g1=new TGraphErrors(100,t,phi_corr[1],dt,dphi_corr[1]);
  g1->Draw("same");
  g1->Fit("f1","R");
  tslopes[1]=-g1->GetFunction("f1")->GetParameter(1);
  errtslopes[1]=g1->GetFunction("f1")->GetParError(1);

  TCanvas *myc3=new TCanvas("myc3");
  myc3->Draw();
  
  char mytitle[80];
  sprintf(mytitle,"E_{#gamma}=%3.2f-%3.2f GeV",7.3+0.6*2-0.3,7.3+0.6*2+0.3);
  TH2F *h3=new TH2F("h3",mytitle,100,0,1.4,100,0,40000.);
  h3->SetXTitle("-t [GeV^{2}]");
  h3->SetYTitle("Acceptance-corrected Yield [counts / 0.04 GeV^{2}");
  h3->Draw();
  TGraphErrors *g2=new TGraphErrors(100,t,phi_corr[2],dt,dphi_corr[2]);
  g2->Draw("same,p"); 
  g2->Fit("f1","R");
  tslopes[2]=-g2->GetFunction("f1")->GetParameter(1);
  errtslopes[2]=g2->GetFunction("f1")->GetParError(1);

  TCanvas *myc4=new TCanvas("myc4");
  myc4->Draw();
  
  TH2F *h4=new TH2F("h4","h4",100,0,1.4,100,0,20000.);
  h4->Draw();

  TGraphErrors *g3=new TGraphErrors(100,t,phi_corr[3],dt,dphi_corr[3]);
  g3->Draw("same"); 
  g3->Fit("f1","R");
  tslopes[3]=-g3->GetFunction("f1")->GetParameter(1);
  errtslopes[3]=g3->GetFunction("f1")->GetParError(1);

  TCanvas *myc5=new TCanvas("myc5");
  myc5->Draw();
  
  TH2F *h5=new TH2F("h5","h5",100,0,1.4,100,0,20000.);
  h5->Draw();
 
  TGraphErrors *g4=new TGraphErrors(100,t,phi_corr[4],dt,dphi_corr[4]);
  g4->Draw("same");
  g4->Fit("f1","R");
  tslopes[4]=-g4->GetFunction("f1")->GetParameter(1);
  errtslopes[4]=g4->GetFunction("f1")->GetParError(1);

  TCanvas *myc6=new TCanvas("myc6");
  myc6->Draw();
  
  TH2F *h6=new TH2F("h6","h6",100,0,1.4,100,0,20000.);
  h6->Draw();
 
  TGraphErrors *g5=new TGraphErrors(100,t,phi_corr[5],dt,dphi_corr[5]);
  g5->Draw("same");
  g5->Fit("f1","R");
  tslopes[5]=-g5->GetFunction("f1")->GetParameter(1);
  errtslopes[5]=g5->GetFunction("f1")->GetParError(1);

  TCanvas *myc7=new TCanvas("myc7");
  myc7->Draw();
  
  TH2F *h7=new TH2F("h7","h7",100,0,1.4,100,0,20000.);
  h7->Draw();

  TGraphErrors *g6=new TGraphErrors(100,t,phi_corr[6],dt,dphi_corr[6]);
  g6->Draw("same"); 
  g6->Fit("f1","R");
  tslopes[6]=-g6->GetFunction("f1")->GetParameter(1);
  errtslopes[6]=g6->GetFunction("f1")->GetParError(1);
  /*
  TCanvas *myc8=new TCanvas("myc8");
  myc8->Draw();
  
  TH2F *h8=new TH2F("h8","h8",100,0,1.4,100,0,20000.);
  h8->Draw();

  TGraphErrors *g7=new TGraphErrors(100,t,phi_corr[7],dt,dphi_corr[7]);
  g7->Draw("same");
  g7->Fit("f1","R"); 
  */
  TCanvas *myc10=new TCanvas("myc10");
  myc10->Draw();
  
  TH2F *h8=new TH2F("h8","t-slope parameter b (yield~e^{bt})",7,7.0,11.2,10,0,6.); 
  h8->SetXTitle("E_{#gamma} [GeV]");
  h8->SetYTitle("b [GeV^{-2}");
  h8->Draw();
  TGraphErrors *g8=new TGraphErrors(7,Egamma,tslopes,dEgamma,errtslopes);
  g8->Draw("same,p"); 

  TCanvas *myc11=new TCanvas("myc11");
  myc9->Draw(); 
  TH2F *h11=new TH2F("h11","E_{#gamma}=8.20-8.80 GeV",100,0,1.4,100,0,0.3); 
  h11->SetXTitle("-t [GeV^{2}]");
  h11->SetYTitle("Acceptance");
  h11->Draw();
  TGraphErrors *eg2=new TGraphErrors(100,t,eff[2],dt,deff[2]);
  eg2->Draw("same,p"); 
}